James A. Purdy

CLINICAL DOSE-VOLUME HISTOGRAM ANALYSIS FOR PNEUMONITIS AFTER 3D TREATMENT FOR NON-SMALL CELL LUNG CANCER (NSCLC)

PURPOSE To identify a clinically relevant and available parameter upon which to identify non-small cell lung cancer (NSCLC) patients at risk for pneumonitis when treated with three-dimensional (3D) radiation therapy. METHODS AND MATERIALS Between January 1991 and October 1995, 99 patients were treated definitively for inoperable NSCLC. Patients were selected for good performance status (96%) and absence of weight loss (82%). All patients had full 3D treatment planning (including total lung dose-volume histograms [DVHs]) prior to treatment delivery. The total lung DVH parameters were compared with the incidence and grade of pneumonitis after treatment. RESULTS Univariate analysis revealed the percent of the total lung volume exceeding 20 Gy (V20), the effective volume (Veff) and the total lung volume mean dose, and location of the tumor primary (upper versus lower lobes) to be statistically significant relative to the development of > or = Grade 2 pneumonitis. Multivariate analysis revealed the V20 to be the single independent predictor of pneumonitis. CONCLUSIONS The V20 from the total lung DVH is a useful parameter easily obtained from most 3D treatment planning systems. The V20 may be useful in comparing competing treatment plans to evaluate the risk of pneumonitis for our individual patient treatment and may also be a useful parameter upon which to stratify patients or prospective dose escalation trials.

Radiation pneumonitis as a function of mean lung dose: an analysis of pooled data of 540 patients.

PURPOSE To determine the relation between the incidence of radiation pneumonitis and the three-dimensional dose distribution in the lung. METHODS AND MATERIALS In five institutions, the incidence of radiation pneumonitis was evaluated in 540 patients. The patients were divided into two groups: a Lung group, consisting of 399 patients with lung cancer and 1 esophagus cancer patient and a Lymph./Breast group with 78 patients treated for malignant lymphoma, 59 for breast cancer, and 3 for other tumor types. The dose per fraction varied between 1.0 and 2.7 Gy and the prescribed total dose between 20 and 92 Gy. Three-dimensional dose calculations were performed with tissue density inhomogeneity correction. The physical dose distribution was converted into the biologically equivalent dose distribution given in fractions of 2 Gy, the normalized total dose (NTD) distribution, by using the linear quadratic model with an alpha/beta ratio of 2.5 and 3.0 Gy. Dose-volume histograms (DVHs) were calculated considering both lungs as one organ and from these DVHs the mean (biological) lung dose, NTDmean, was obtained. Radiation pneumonitis was scored as a complication when the pneumonitis grade was grade 2 (steroids needed for medical treatment) or higher. For statistical analysis the conventional normal tissue complication probability (NTCP) model of Lyman (with n=1) was applied along with an institutional-dependent offset parameter to account for systematic differences in scoring patients at different institutions. RESULTS The mean lung dose, NTDmean, ranged from 0 to 34 Gy and 73 of the 540 patients experienced pneumonitis, grade 2 or higher. In all centers, an increasing pneumonitis rate was observed with increasing NTDmean. The data were fitted to the Lyman model with NTD50=31.8 Gy and m=0.43, assuming that for all patients the same parameter values could be used. However, in the low dose range at an NTDmean between 4 and 16 Gy, the observed pneumonitis incidence in the Lung group (10%) was significantly (p=0.02) higher than in the Lymph./Breast group (1.4%). Moreover, between the Lung groups of different institutions, also significant (p=0.04) differences were present: for centers 2, 3, and 4, the pneumonitis incidence was about 13%, whereas for center 5 only 3%. Explicitly accounting for these differences by adding center-dependent offset values for the Lung group, improved the data fit significantly (p < 10(-5)) with NTD50=30.5+/-1.4 Gy and m=0.30+/-0.02 (+/-1 SE) for all patients, and an offset of 0-11% for the Lung group, depending on the center. CONCLUSIONS The mean lung dose, NTDmean, is relatively easy to calculate, and is a useful predictor of the risk of radiation pneumonitis. The observed dose-effect relation between the NTDmean and the incidence of radiation pneumonitis, based on a large clinical data set, might be of value in dose-escalating studies for lung cancer. The validity of the obtained dose-effect relation will have to be tested in future studies, regarding the influence of confounding factors and dose distributions different from the ones in this study.

A prospective study of salivary function sparing in patients with head-and-neck cancers receiving intensity-modulated or three-dimensional radiation therapy: initial results☆

OBJECTIVES In a prospective clinical study, we tested the hypothesis that sparing the parotid glands may result in significant objective and subjective improvement of xerostomia in patients with head-and-neck cancers. The functional outcome 6 months after the completion of radiation therapy is presented. METHODS AND MATERIALS From February 1997 to February 1999, 41 patients with head-and-neck cancers were enrolled in a prospective salivary function study. Inverse-planning intensity-modulated radiation therapy (IMRT) was used to treat 27 patients, and forward-planning three-dimensional radiation therapy in 14. To avoid potential bias in data interpretation, only patients whose submandibular glands received greater than 50 Gy were eligible. Attempts were made to spare the superficial lobe of the parotid glands to avoid underdosing tumor targets in the parapharyngeal space; however, the entire parotid volume was used to compute dose-volume histograms (DVHs) for this analysis. DVHs were computed for each gland separately. Parotid function was assessed objectively by measuring stimulated and unstimulated saliva flow before and 6 months after the completion of radiation therapy. Measurements were converted to flow rate (mL/min) and normalized relative to that before treatment. The corresponding quality-of-life (QOL) outcome was assessed by five questions regarding the patients oral discomfort and eating/speaking problems. RESULTS We observed a correlation between parotid mean dose and the fractional reduction of stimulated saliva output at 6 months after the completion of radiation therapy. We further examined whether the functional outcome could be modeled as a function of dose. Two models were found to describe the dose-response data well. The first model assumed that each parotid gland is comprised of multiple independent parallel functional subunits (corresponding to computed tomography voxels) and that each gland contributes equally to overall flow, and that saliva output decreases exponentially as a quadratic function of irradiation dose to each voxel. The second approach uses the equivalent uniform dose (EUD) metrics, which assumes loss of salivary function with increase in EUD for each parotid gland independently. The analysis suggested that the mean dose to each parotid gland is a reasonable indicator for the functional outcome of each gland. The corresponding exponential coefficient was 0.0428/Gy (95% confidence interval: 0.01, 0.09). The QOL questions on eating/speaking function were significantly correlated with stimulated and unstimulated saliva flow at 6 months. In a multivariate analysis, a toxicity score derived from the model based on radiation dose to the parotid gland was found to be the sole significant predictive factor for xerostomia. Neither radiation technique (IMRT vs. non-IMRT) nor chemotherapy (yes or no) independently influenced the functional outcome of the salivary glands. CONCLUSION Sparing of the parotid glands translates into objective and subjective improvement of both xerostomia and QOL scores in patients with head-and-neck cancers receiving radiation therapy. Modeling results suggest an exponential relationship between saliva flow reduction and mean parotid dose for each gland. We found that the stimulated saliva flow at 6 months after treatment is reduced exponentially, for each gland independently, at a rate of approximately 4% per Gy of mean parotid dose.

Preliminary report of toxicity following 3D radiation therapy for prostate cancer on 3DOG/RTOG 9406

PURPOSE A prospective Phase I dose escalation study was conducted to determine the maximally-tolerated radiation dose in men treated with three-dimensional conformal radiation therapy (3D CRT) for localized prostate cancer. This is a preliminary report of toxicity encountered on the 3DOG/RTOG 9406 study. METHODS AND MATERIALS Each participating institution was required to implement data exchange with the RTOG 3D quality assurance (QA) center at Washington University in St. Louis. 3D CRT capabilities were strictly defined within the study protocol. Patients were registered according to three stratification groups: Group 1 patients had clinically organ-confined disease (T1,2) with a calculated risk of seminal vesicle invasion of < 15%. Group 2 patients had clinical T1,2 disease with risk of SV invasion > or = 15%. Group 3 (G3) patients had clinical local extension of tumor beyond the prostate capsule (T3). All patients were treated with 3D techniques with minimum doses prescribed to the planning target volume (PTV). The PTV margins were 5-10 mm around the prostate for patients in Group 1 and 5-10 mm around the prostate and SV for Group 2. After 55.8 Gy, the PTV was reduced in Group 2 patients to 5-10 mm around the prostate only. Minimum prescription dose began at 68.4 Gy (level I) and was escalated to 73.8 Gy (level II) and subsequently to 79.2 Gy (level III). This report describes the acute and late toxicity encountered in Group 1 and 2 patients treated to the first two study dose levels. Data from RTOG 7506 and 7706 allowed calculation of the expected probability of observing a > or = grade 3 late effect more than 120 days after the start of treatment. RTOG toxicity scores were used. RESULTS Between August 23, 1994 and July 2, 1997, 304 Group 1 and 2 cases were registered; 288 cases were analyzable for toxicity. Acute toxicity was low, with 53-54% of Group 1 patients having either no or grade 1 toxicity at dose levels I and II, respectively. Sixty-two percent of Group 2 patients had either none or grade 1 toxicity at either dose level. Few patients (0-3%) experienced a grade 3 acute bowel or bladder toxicity, and there were no grade 4 or 5 toxicities. Late toxicity was very low in all patient groups. The majority (81-85%) had either no or mild grade 1 late toxicity at dose level I and II, respectively. A single late grade 3 bladder toxicity in a Group 2 patient treated to dose level II was recorded. There were no grade 4 or 5 late effects in any patient. Compared to historical RTOG controls (studies 7506, 7706) at dose level I, no grade 3 or greater late effects were observed in Group 1 and Group 2 patients when 9.1 and 4.8 events were expected (p = 0.003 and p = 0.028), respectively. At dose level II, there were no grade 3 or greater toxicities in Group 1 patients and a single grade 3 toxicity in a Group 2 patient when 12.1 and 13.0 were expected (p = 0.0005 and p = 0.0003), respectively. Multivariate analysis demonstrated that the relative risk of developing acute bladder toxicity was 2.13 if the percentage of the bladder receiving > or = 65 Gy was more than 30% (p = 0.013) and 2.01 if patients received neoadjuvant hormonal therapy (p = 0.018). The relative risk of developing late bladder complications also increased as the percentage of the bladder receiving > or = 65 Gy increased (p = 0.026). Unexpectedly, there was a lower risk of late bladder complications as the mean dose to the bladder and prescription dose level increased. This probably reflects improvement in conformal techniques as the study matured. There was a 2.1 relative risk of developing a late bowel complication if the total rectal volume on the planning CT scan exceeded 100 cc (p = 0.019). CONCLUSION Tolerance to high-dose 3D CRT has been better than expected in this dose escalation trial for Stage T1,2 prostate cancer compared to low-dose RTOG historical experience. With strict quality assurance standards and review, 3D CRT can be safely studied in a co

Radiation therapy alone in the treatment of carcinoma of the uterine cervix. II. Analysis of complications

A retrospective analysis was carried out on 811 patients with histologically proven invasive carcinoma of the uterine cervix treated with irradiation alone. A correlation was made of the doses of irradiation delivered to the pelvic organs with external beam and intracavitary insertions. Approximately 3% of the patients exhibited grade 2 gastrointestinal complications, and 2% developed grade 2 urinary complications; 5% of the patients developed grade 3 gastrointestinal complications, and 3% developed grade 3 urinary complications. Other types of complications, primarily grade 2, such as vaginal necrosis, pelivic abscess, thrombophlebitis, etc, were seen in approximately 5% of the patients. Thus, the total percentage of patients developing grade 2 complicatins was 10% and grade 3 complications, approximately 8%. About 25% of the patients who had complications showed more than one sequela. The most frequently observed grade 2 complications were proctitis, cystitis, vaginal stenosis, and partial small bowel obstruction which were treated with conservative management. Grade 3 complications required surgical treatment and consisted most frequently of ureteral stricture, vesicovaginal fistula, rectovaginal fistula, sigmoid stricture, small bowel obstruction, proctitis, and large rectal ulcers. The most significant factor affecting the appearance of complications was the total dose of irradiation delivered to the pelvic organs by the whole pelvis external irradiation and intracavitary insertions. With maximum total doses up to 8000 rad the incidence of grade 2 and 3 complications was less than 5%. However, with higher doses the incidence of complications increased to 10% to 15%. In patients receiving total doses of 6000 rad to the bladder or rectum, more complications were noted when only one intracavitary insertion was performed, as compared with two or three. Eighty percent of the rectosigmoid complications occurred within 30 months of initial therapy, in contrast to 48 months for the urinary complications. Patients who developed complications had survival rates comparable to those without complications. This underscores the need to rapidly institute treatment on patients who have severe injury after radiation therapy. Even though it is difficult to determine the exact total dose delivered to a specific volume within the pelvis, the current study strongly indicates that dose calculations to specific anatomical points may be reliable parameters to use in modifying treatment techniques to deliver doses of irradiation that will not exceed tolerance limits for the pelvic structures, when treating patients with carcinoma of the uterine cervix with irradiation alone.

Radiation therapy alone in the treatment of carcinoma of uterine cervix I. Analysis of tumor recurrence

This is a retrospective analysis with emphasis on the patterns of failure in 849 patients with histologically proven invasive carcinoma of the uterine cervix treated with irradiation alone. In 281 patients with Stage IB tumors, the total incidence of pelvic failure was 6.4% (two without and 16 combined with distant metastasis). In 88 patients with Stage IIA, 12.5% failed in the pelvis (one without and ten combined with distant metastasis). The total pelvic failure rate in Stage IIB was 17.4% (22 without and 22 combined with distant metastasis). In 212 patients with Stage III, the overall pelvic failure rate was 35.8% (31 without and 45 combined with distant metastasis). Approximately 25% of the pelvic recurrences were central (cervix or vagina) and 75% parametrial. The overall incidence of distant metastasis was 13.5% for Stage IB, 27.3% for Stage IIA, 23.8% for Stage IIB, and 39.6% in Stage III. Higher doses of irradiation delivered to the medial and lateral parametrium with external beam irradiation and intracavitary insertions were correlated with a lower incidence of parametrial failures in all stages, except IB. In Stage IIA, medial parametrial doses below 9000 rad resulted in 10/78 = 12.8% pelvic failures, in contrast to one recurrence in 10 patients treated with doses over 9000 rad. In Stage IIB, doses below 9000 rad yielded a pelvic recurrence rate of 36/203 (17.7%) compared to 5/49 (10.2%) with higher doses. In Stage III there were 66/167 (39.5%) recurrences with doses below 9000 rad and 10/44 (22.7%) with larger doses. Statistically significant differences were observed among the Stage IIB (P = 0.02) and III patients (P = 0.005) respectively. The lateral parametrial dose also showed some correlation with tumor control, although the differences were not statistically significant. The survival in patients with Stage IIB and III was 10% higher in the patients treated with higher parametrial doses. However, the differences are not statistically significant. These results strongly suggest that higher doses of irradiation must be delivered to patients with Stage IIB and III, but improvement in tumor control must be weighed against an increasing number of complications. Factors other than the total doses of irradiation, such as the characteristics of the tumor and the quality of the intracavitary insertion influence the therapeutic results in irradiation of carcinoma of the uterine cervix. Other therapeutic approaches must be designed to improve the effect of irradiation in the tumor without further injury to the normal tissues. Hypoxic cell sensitizers, hyperthermia and high LET particles are under investigation.

Gross tumor volume, critical prognostic factor in patients treated with three-dimensional conformal radiation therapy for non-small-cell lung carcinoma

PURPOSE Three-dimensional conformal radiation therapy (3D-CRT) has recently become widely available with applications for patients with non-small-cell lung cancer (NSCLC). These techniques represent a significant advance in the delivery of radiotherapy, including improved ability to delineate target contours, choose beam angles, and determine dose distributions more accurately than were previously available. The purpose of this study is to identify prognostic factors in a population of NSCLC patients treated with definitive 3D-CRT. METHODS AND MATERIALS Between March 1991 and December 1998, 207 patients with inoperable NSCLC were treated with definitive 3D-CRT. Tumor targets were contoured in multiple sections from a treatment planning computed tomography (CT) scan. Three-dimensional treatment volumes and normal structures were reconstructed. Doses to the International Commission on Radiation Units and Measurements (ICRU) reference point ranged from 60 to 83.85 Gy with a median dose of 70 Gy. The median dose inhomogeneity was +/- 5% across planning target volume. Outcome was analyzed by prognostic factors for NSCLC including pretreatment patient and tumor-related factors (age, gender, race, histology, clinical stage, tumor [T] stage, and node [N] stage), parameters from our 3D-CRT system (gross tumor volume [GTV] in cm3), irradiation dose prescribed to isocenter, volume of normal lung exceeding 20 Gy (V20), and treatment with or without chemotherapy. The median follow-up time was 24 months (range, 7.5 months to 7.5 years). RESULTS One and two-year overall survival rates for the entire group were 59% and 41%, respectively. Overall survival, cause-specific survival, and local tumor control were most highly correlated with the GTV in cm3. On multivariate analysis the independent variable most predictive of survival was the GTV. Traditional staging such as T, N, and overall clinical staging were not independent prognostic factors. Patients receiving ICRU reference doses > or =70 Gy had better local control and cause-specific survivals than those treated with lower doses (p = 0.05). Increased irradiation dose did not improve overall survival. CONCLUSIONS GTV as determined by CT and 3D-CRT planning is highly prognostic for overall and cause-specific survival and local tumor control and may be important in stratification of patients in prospective therapy trials. T, N, and overall stage were not independent prognostic factors in this population of patients treated nonsurgically. The value of dose escalation beyond 70 Gy should be tested prospectively by clinical trial.

Toxicity after three-dimensional radiotherapy for prostate cancer on RTOG 9406 dose Level V

PURPOSE This is the first report of toxicity outcomes at dose Level V (78 Gy) on Radiation Therapy Oncology Group 9406 for Stages T1-T2 adenocarcinoma of the prostate. METHODS AND MATERIALS A total of 225 patients were entered in this cooperative group, Phase I-II dose-escalation trial of three-dimensional conformal radiotherapy for localized carcinoma of the prostate treated to a dose of 78 Gy (Level V). Of these patients, 219 were analyzed for acute and 218 for late toxicity. A minimum of 2 Gy/fraction was prescribed to the planning target volume (PTV). Patients were stratified according to the risk of seminal vesicle invasion as determined by Gleason score and presenting prostate-specific antigen level. Group 1 patients had clinical Stages T1-T2 tumors with a seminal vesicle invasion risk of <15%. Group 2 patients had clinical Stages T1-T2 tumors with a seminal vesicle invasion risk of >/=15%. Patients in Group 1 were prescribed 78 Gy to a prostate PTV. Patients in Group 2 were prescribed 54 Gy to the prostate and seminal vesicles (PTV1) followed by a boost to the prostate only (PTV2) to 78 Gy. PTV margins of between 5 and 10 mm were required. The average time at risk for late Grade 3+ toxicity after therapy completion was 23.2 and 23.1 months for Groups 1 and 2, respectively. The frequency of Grade 3 or worse late effects was compared with a similar group of patients treated in Radiation Therapy Oncology Group (RTOG) studies 7506 and 7706, with length of follow-up adjustments made for the interval from therapy completion. A second comparison was made with 170 patients treated to dose Level III (79.2 Gy in 1.8 Gy/fraction) to see whether the fraction size affected toxicity. Unlike other dose levels, patients treated at dose Level III had treatment prescribed as a minimum to the gross tumor volume. This effectively lowered the volume of the rectum treated to the study dose. RESULTS Acute toxicity at dose Level V (78 Gy) was remarkably low, with Grade 3 acute effects reported in only 4% of Group 1 and 2% of Group 2 patients. No Grade 4 or 5 acute toxicity was reported. There was no statistically significant difference in rates of acute toxicities in patients who were treated to 79.2 Gy at 1.8 Gy/fraction or 78 Gy at 2.0 Gy/fraction. Late toxicity continues to be low compared with RTOG historical controls. The observed rate of Grade 3 or worse late effects for Group 1 (6 cases) was significantly lower (p = 0.0042) than the 18.2 cases that would have been expected from the historical control. The observed rate for Group 2 (8 cases) was lower than the 15.5 cases expected, but this difference was not statistically significant (p = 0.06). A trend was noted that Group 2 patients treated on dose Level V had more late Grade 3 or worse toxicity than patients treated to a similar dose on Level III (7% vs. 1%, p = 0.06). A significantly (p < 0.0001) greater incidence of late Grade 2 or greater toxicity occurred in patients treated at dose Level V (30% and 33% for Groups 1 and 2, respectively) than at dose Level III (13% and 9% for Groups 1 and 2, respectively). The longer follow-up at dose Level III suggests these differences may increase with additional follow-up. CONCLUSION Tolerance to three-dimensional conformal radiotherapy with 78 Gy in 2-Gy fractions remains better than expected compared with historical controls. The magnitude of any effect from fraction size and treatment volume requires additional follow-up.

Dose-response analysis for nasopharyngeal carcinoma: an historical perspective.

Historical review of 118 patients with nasopharyngeal cancer treated in our institution from 1950–1978 showed a 20% improvement in tumor control for patients irradiated during the most recent period (1974–1978). This improvement was attributed to prescription of higher doses of radiation as well as improvements in technical accuracy and dose delivery to the tumor during that period. Rates of severe and mild complications were comparable and survival was not significantly altered over time despite improved tumor control. Within the range of doses delivered, there was no improvement in tumor control with increasing doses of radiation for small or large nasopharyngeal carcinomas. The dose—response analysis for tumor control was less than ideal because a number of prerequisites were lacking and because the study extended over a 28‐year span during which there were significant changes in technology and physician orientation.

Preliminary results of a prospective trial using three dimensional radiotherapy for lung cancer

PURPOSE To evaluate the preliminary results of a prospective trial using three-dimensional (3D) treatment for lung cancer. METHODS AND MATERIALS Seventy patients with inoperable Stage I through IIIB lung cancer were treated with three-dimensional thoracic irradiation with or without chemotherapy (35% received chemotherapy). Total prescribed dose to the tumor ranged from 60-74 Gy (uncorrected for lung density). All patients were evaluated for local control, survival, and development of pneumonitis. These parameters were evaluated in respect to and compared with three-dimensional parameters used in their treatment planning. RESULTS With a minimum follow-up of 6 to 30 months, the 2-year cause-specific survival rate for Stages I and II was 90% and 53% for Stage III (no difference between Stages IIIA and IIIB). Patients with local tumor control had a better 2-year overall survival rate (47%) than those with local failure (31%). Volumetrically heterogeneously calculated doses were important to the accurate delineation of dose-volume coverage as there was a wide range of discrepancies between a homogeneously prescribed point dose calculation and the heterogeneously calculated volume coverage of that prescription. High-grade pneumonitis was correlated with the location of the tumor with lower lobe tumors having a much higher risk than those with upper lobe tumors. A critical volume effect and threshold dose were apparent in the development of high-grade pneumonitis. CONCLUSIONS Three-dimensional therapy for lung cancer has been practically implemented at the Mallinckrodt Institute of Radiology and shows promising results in our preliminary analysis. The incidence of high-grade pneumonitis, however, warrants careful selection of patients for future dose escalation. Future dose escalation trials in lung cancer should be directed to volumes that limit the amount of elective nodal irradiation. However, the volume of necessary elective nodal irradiation remains unknown and should be studied prospectively. Dose escalation trials are indicated and may be facilitated by smaller target volumes.